The present invention relates to a tape cassette and more particularly to a tape cassette provided with a locking mechanism for locking a front lid disposed to close the front portion of a cassette case body and adapted to protect the tape mounted in the cassette case.
Generally, a tape cassette, for example, a tape cassette adapted to be mounted in a video cassette deck is provided with a front lid disposed to the front portion of a cassette case body to protect a magnetic tape, called merely "a tape" hereinafter, which is guided outside the front portion of the case body. The front lid is secured to the front portion of the case body to be pivotable to open or close the front lid in such a manner that, when the cassette is not used, the front lid is locked so as to cover the outside of the tape and that, when the cassette is mounted in the video deck, the locking mechanism is released. Thus the front lid is pivoted upwardly to open the same, and the tape is drawn out from the front portion of the case body towards a rotating head.
A general tape cassette for a video cassette deck of the described type is shown in FIGS. 5 and 6. Referring to FIGS. 5 and 6, a main case body 2 of a tape cassette 1 is substantially composed of upper and lower case halves 2a and 2b which are mated with each other and secured to each other by means of screws. The case body 2 is generally made of a plastic material. A pair of tape reels 4 and 4 around which a tape 3 is reeled, are housed in the case body 2 to be rotatable in substantially a bilaterally symmetrical arrangement. The tape 3 unwound from one of the reels 4 is exposed through the front portion of the case body 2 and then taken up by the other reel.
Transparent leader tapes are connected to both ends of the tape 3. A through hole 5 is formed at the front central portion of the case half 2b. When the tape cassette 1 is mounted in the video deck, a light detecting lamp 6 for detecting light is guided into the through hole .5 and the detected light from the light detecting lamp 6 is transmitted to a photosensor through the transparent leader tape thereby detecting the end of the tape 3.
A front lid 7 located at the front portion of the case body 2 to protect the tape 3 is provided with bilateral side ends 7a and 7a, which are secured to the front portions of the bilateral side walls of the case body 2 to be pivotable about pins 7b and 7b. The front lid 7 is urged to be closed by means of a coil spring 8 mounted on the pin 7b and is locked by means of a lid closing mechanism.
A member 9 for operating the front lid locking mechanism of the tape cassette 1 is secured to a portion on the side of the cassette deck, and when the tape cassette 1 has been mounted in the cassette deck, the locking mechanism is released by means of the member 9. A lever 10 provided for the cassette deck and adapted to operate as a front lid releasing member is guided into a vertical groove 11 formed in the front portion of the case body 2 thereby upwardly opening the front lid against the urging force of the coil spring 8.
The front lid locking mechanism described above will be explained in further detail hereunder, with reference to FIG. 7.
Referring to FIG. 7, the lower case half 2b constituting part of the case body 2 is provided with a chamber 12 for mounting a lock plate 13. The lock plate 13 is provided with a locking claw 13a and a projection 13b for releasing the locking of the front lid 7. The lock plate 13 is supported by walls of the lock plate mounting chamber 12 so as to be pivotable about pivot portions 13c and 13c in the shape of pins formed integrally with the lock plate 13 at the upper portion thereof, the pivot portions 13c being merely called pins 13c hereinafter. The lock plate 13 is urged by an additionally disposed return spring 14 to a locking position on a front wall side of the chamber 12 so as to project the locking claw 13a outwardly through a hole formed in the front wall 12a of the chamber 12. The projected end of the locking claw 13a is engaged with the inner surface of one side end 7a of the front lid 7 thereby locking the same.
The front lid locking mechanism is released by inwardly pressing the projection 13b which projects outwardly of the case body 2 through a notch formed in the front wall 12a of the lock plate mounting chamber 12.
With the front lid locking mechanism of the type described, however, the mounting of the return spring 14 involves troublesome work and the tape cassette itself includes many parts or members that have to be assembled.
In order to obviate the problems described above with reference to FIG. 7, there is provided another lid locking mechanism for a tape cassette as disclosed in Japanese Utility Model Publication No. 60-20210, which will be described hereunder with reference to FIG. 8, in which a spring member is preliminarily formed integrally with the lock plate.
Referring to FIG. 8, showing a perspective view of a front lid locking mechanism in a disassembled state, a lock plate 15 is provided with a locking claw 15a and a projection 15b which are similar to those 13a and 13b of the lock plate 13 of FIG. 7. A thin plate-like spring member 15e of substantially U-shape is integrally formed with the lock plate 15 at the lower portion of an inner surface of the lock plate 15 in a cantilevered manner so as to extend upwardly as shown in FIG. 8. The lock plate 15 is inserted into a lock plate mounting chamber 12 similar to that of FIG. 7 from the upper side thereof along the front wall 12a of the chamber 12 until pivot pins 15c integrally formed at the upper bilateral end portions of the lock plate 15 come into engagement with grooves 12b formed in the upper portions of the side walls of the mounting chamber 12.
As described, when the lock plate 15 is inserted into the mounting chamber 12, the plate spring member 15e abuts against the inner surface of a rear wall 12c of the chamber 12 while elastically deformed. The lock plate 15 is lowered under the state in which the extending free end 15e.sub.1 of the plate spring member 15e, always abuts elastically against the inner surface of the rear wall 12c of the mounting chamber 12. According to the provision of the plate spring member 15e, the lock plate 15 is urged forward to the locking position thereof on the side of the front wall 12a. Under this condition, the locking claw 15a projects outwardly through a hole formed in the front wall 12a of the mounting chamber 12 so as to come into engagement with the inner surface of the one side end 7a of the front lid 7 to lock the same. The locking mechanism of FIG. 8 can also be released by inwardly pressing the projection 15b as described with reference to the mechanism shown in FIG. 7.
However, with the lid locking mechanism for a tape cassette of FIG. 8, the plate like spring member 15e always abuts elastically against the inner surface of the rear wall 12c of the lock plate mounting chamber 12, so that the plate spring member 15e may be adversely deformed or may have its elastic properties changed with the lapse of time. In an adverse case, the front lid 7 cannot be securely locked and closed, whereby the tape 3 accommodated in the cassette 1 cannot be sufficiently protected.